The present invention is directed to a vehicle frame for a work vehicle and methods for manufacturing the frame.
A frame structure where the cabin frame is bolted to the vehicle frame is disclosed, for example, in JP2001-191958 (paragraph numbers 0027, 0029, FIG. 1, FIG. 7) and also a structure driving cabin is supported at the back of the vehicle body through a vibration control connection portion is disclosed, for example, in JP2006-36073 (paragraph number 0013, FIG. 1, FIG. 2, FIG. 5).
Other examples of the cabin structure for work vehicles include one, for example, JP H11-91638 (paragraph number 0023, FIGS. 1-5), where each corner of the cabin frame is formed so that the corners form sharp angles with a pair of right and left vertical front frames, a pair of right and left vertical rear frames, a pair of right and left upper fore-and-aft frames extending in the fore-and-aft direction, a pair of right and left lower fore-and-aft frames extending in the fore-and-aft direction, a pair of front and rear laterally extending upper lateral frame, a single lateral lower lateral frame, and a plurality of connecting member that connect ends of corresponding frames, and one, for example, JP 2005-212521 (paragraph number 0016, FIGS. 1-6), where each corner of the cabin frame is formed so that the corners form sharp angles with a pair of right and left vertical front frames, a pair of right and left vertical rear frames, a pair of right and left upper fore-and-aft lateral frames extending in the fore-and-aft direction between the corresponding upper portions of the front vertical frame and the rear vertical frame, and a pair of right and left lower fore-and-aft lateral frames extending in the fore-and-aft direction between the corresponding lower portions of the front vertical frame and the rear vertical frame.
With the above-mentioned structure, for a cabin frame (driving cabin) to have sufficient strength to protect the passenger, and for the vehicle frame (vehicle body) to be able to mount the cabin frame, the cabin frame needs to be equipped with structurally strong members and reinforcing members to provide them with sufficient strength. As a result, the component parts of the frame increase in number and the frame structure becomes more complicated, resulting in an increased overall weight of the vehicle with a higher manufacturing cost, lower productivity and less efficient fuel consumption, etc.
In the structure described above, because the cabin frame is formed so that each corner thereof forms a sharp angle, stress tends to be concentrated on each corner when an outside force is applied to the cabin frame, which tends to increase the possibility of deforming the cabin frame due to concentration of stress.